An assay device is important in many biological assays, such as for detecting an analyte in a liquid sample. A desirable feature of an assay device is the durability of the plate and maintenance of the reagent in the plate for accurate assay results. For example, a design for an assay device is a sample plate comprising molded wells with fingers that protrude up from the bottom of the well and into which a reagent bead is dispensed, and the reagent bead can be captured in the fingers. However, as reagent beads are free to move up and down within the finger height, a reagent bead may become stuck at an undesired height during a processing or reading step, which can lead to an inaccurate assay result. Furthermore, any movement of, or damage to, the fingers could result in a reagent bead becoming stuck at an undesired height. The fingers also protrude from the base which makes them susceptible to damage particularly during pipetting and washing stages.
Another desirable feature of an assay device is the ability to perform multiple assays at once, or the ability to multiplex. For example, an assay device with a high density of wells for a sample plate allows an increased number of assays to be performed on a single plate. Another desirable characteristic of an assay device is the ability to use a minimal amount of reagents and sample, as well as the prevention of crosstalk between different samples during multiplexing.
Another desirable aspect of an assay device is the ease in manufacturing. For example, a sample well with molded fingers is relatively complex to manufacture and can suffer from unreliability issues during manufacture. The long thin fingers are difficult to form by molding and would be prone to damage during manufacture or during use. The fingers also have a feature at the top which in a mould tool would be an undercut. When the part is ejected off the tool the fingers must bend for the feature to get past the tool material. Such a manufacturing process is generally undesirable due to unreliability issues. Furthermore, any change in the process parameters is likely to affect the ability to release the part from the tool and leave the part intact to the correct mechanical tolerances. The position of the fingers relative to each other would be critical to allow the reagent bead to move up and down correctly and also to ensure that the reagent bead does not come out of the top of the fingers. This would be very difficult, in practice, to control in a mass production environment. The design of the single bead arrangement is also completely different to the design of the multi-well arrangement. As a result, completely different tool designs would be required which again would greatly increase the complexity of manufacture. In a high volume manufacturing environment the combination of the design features and quality assurance concerns would make the sample plates excessively expensive to produce.
Thus, there is a need for an assay device with one or more of these desirable features. Provided herein is a sample plate system, and methods of using the system, that meets these needs and provides related advantages as well.